PC Stephen Dennis was walking his dog near Hubbards Hills the morning after the killings when he tried to detain suspected killer Daniel Boulton, 30.
Police had issued an appeal to find Boulton after Bethany Vincent, 26, and her nine-year-old son Darren Henson, known to all his family as DJ, were found dead in their home at 182 High Holme Road, Louth, at 8pm on May 31.
The court heard that both had been “brutally stabbed” by Boulton who fled through the streets of Louth, leaving an unharmed nine-month-old child crawling around the property.
Lincoln Crown Court heard Boulton spent the night on the run after forcing entry into an empty cottage at Hubbards Hills on the outskirts of Louth where he allegedly stole some alcohol, clothing, and food.
Katherine Goddard QC, prosecuting, told the jury Boulton left a note stating: “I Daniel Boulton take full responsibility of 182”.
However the following morning Boulton was recognised by PC Dennis who was walking his dog close to the cottage and was aware of the police appeal.
Miss Goddard said: “On the morning of June 1, an off duty police officer, PC Dennis, was walking his dog close to the bungalow.
“He saw Mr Boulton was talking to another dog walker, an elderly woman, causing him to be concerned for her safety, so he approached Mr Boulton.
“There was a short confrontation, blows being exchanged between the two men, before Mr Boulton ran off pursued by PC Dennis and there was a second confrontation.
“During the second confrontation Mr Boulton pulled out a knife and stabbed PC Dennis in the leg.
“Once again Mr Boulton ran off but PC Dennis managed to contact his colleagues and soon the area was flooded with police.”
Boulton was found at nearby Hallington House Farm and made determined efforts to escape, trying to get in a car.
However, he was cornered in a barn and tasered after trying to get some of the armed officers to shoot him.
Miss Goddard said while it was not disputed that Boulton physically carried out the stabbings, it was his case that at the time he was suffering from a recognised mental health condition which substantially impaired his ability to form a rational judgement and to exercise self control.
But Miss Goddard said it was the prosecution case that Boulton had previously expressed his intention to kill and made his way to Louth on foot where he chose not to harm the other child in the house.
“It was a man who had planned his actions, who was fully in control of them,” Miss Goddard added.
“At around 8pm on the evening of May 31 a young woman and her nine-year-old son were brutally stabbed to death in their home in Louth.”
The jury heard Boulton was the ex-partner of Bethany and their relationship which began happily in March 2019 had deteriorated and become marked by violence from Boulton towards Bethany, and later towards her parents.
Boulton was made the subject of a restraining order, precluding him from contacting Bethany.
Miss Goddard added: “A further restraining order was made in February 2021.
“But despite both those orders, Mr Boulton continued to contact Bethany by telephone, text message, social media, and by unannounced and uninvited visits to her home.
“None of that contact was sought by Bethany, and she and DJ were due to move to a new home at an address unknown to Mr Boulton only days after their killing.”
She added: “Social services became involved with Bethany’s family after her first complaint to the police of domestic violence in November 2020.
“Their concerns about the family related only to the risk Mr Boulton presented to the family as he had expressed a hatred towards DJ who had been diagnosed with autism.”
In the early part of 2021, Mr Boulton was allocated a room at a hostel in Skegness and he was living there on May 31.
That same weekend, DJ had spent the night with his father.
Miss Goddard told the jury: “Shortly after 8pm on the evening of May 31, members of the public saw Mr Boulton on High Holme Road.
“He was seen running from an alleyway leading to the rear of number 182. He seemed flushed, agitated and called out to the witnesses ‘to call an ambulance as someone had been stabbed inside.’
“He then disappeared, not waiting for the emergency services to arrive.
“When paramedics arrived in response to the call from the witnesses, they made their way into the house.
“In the front room, the room with the bay windows overlooking the roundabout they found Bethany. She was lying on the floor, curled up, clearly already dead.
“Upstairs, they found DJ in his bedroom, also clearly dead.”
Postmortem results showed both Bethany and DJ had suffered multiple stab and blunt force injuries, including a 20cm stab wound to Bethany.
Miss Goddard said a nine-month-old child was also found unharmed, “but obviously distressed crawling through the house.”
Police quickly identified Boulton as a suspect and dashcam footage from a passing motorist showed two girls playing in the street had witnessed some of the events at the property.
Miss Goddard said: “Through an open window they heard a woman’s voice shouting ‘call the police’ and they saw two other people nearby apparently not doing anything, so they crossed the road to have a look through the bay window.
“They saw a man come up, Mr Boulton come up, with what appeared to be a rope in his hand standing alongside a woman holding a baby.”
Boulton, 30, of Alexandra Road, Skegness, denies murdering Bethany Vincent, 26, and her nine-year-old son Darren Henson in Louth, Lincs, on 31 May last year.
He also denies assaulting PC Stephen Dennis with intent to resist arrest on June 1 and a further offence of burglary at Hubbards Hills Cottage in Halfpenny Lane, Louth, where it is alleged clothing, food and drink were stolen between May 30 and June 2 last year.
• The trial continues.